Prostacyclin in the body is a local hormone mainly produced in the inside walls of the arteries and is an important factor in adjusting the functions of the body due to its powerful bioactivities, for example, activity in suppressing platelet aggregation and activity of vasodilation. It has been tried to use as a pharmaceutical. (P. J. Lewis & J. O. Grady, "Clinical Pharmacology of Prostacyclin", Raven Press, N.Y., 1981).
However, natural prostacyclin has an extremely easily hydrolyzed enol-ether bond in the molecule, so easily is inactivated in neutral or acid conditions and therefore cannot be said to be a preferable compound for a pharmaceutical due to its chemical instability. Therefore, chemically stable synthetic prostacyclin derivatives having bioactivity similar to natural prostacyclin have been studied at home and abroad (see R. C. Nickolson et al., Medicinal Research Reviews, vol. 5, p. 1, 1985). Among these, an isocarbacyclin, which is obtained by replacing the 6,9-position oxygen atom of prostacyclin with a methine group --CH.dbd.group) and converting the 5,6-position double bond to a single bond, is a derivative which is chemically extremely stable and has a bioactivity comparable to natural prostacyclin. Application for pharmaceuticals is now being studied.
However, due to its powerful action in suppressing platelet aggregation and its peripheral vasodilation action, experiments as a clinical application of prostacyclin, are being tried to use for chronic arterial occlusion and other thrombotic disorders. Beraprost (tradename) ("The Japanese Journal of Clinical and Experimental Medicine", vol. 67, p. 574, 1990), Iloprost (tradename) ("The Japanese Journal of Clinical and Experimental Medicine", vol. 68, p. 1836, 1991), and other examples have been reported. The active ingredient of these, prostacyclin derivatives, however, is different in structure from the active ingredient of the present invention, that is, isocarbacyclin. The form of the preparation is also very different.
On the other hand, as a stabilized lipid preparation of prostaglandin derivatives, in recent years a lipid emulsion containing PGE.sub.1 or PGA.sub.1 has been proposed for the purpose of its vasodilation action, suppressing action of platelet aggregation and blood pressure reducing action etc. (see Japanese Unexamined Patent Publication (Kokai) No. 58-222014, Japanese Unexamined Patent Publication (Kokai) No. 59-141518, and Ann. Rheum. Diseases, 41 263 (1982); J. Pharm. Pharmacol., 35, 398 (1983)). This technique of making lipid preparations has been applied also to anticancer agents and proposals have been made to raise the selective transfer of the anticancer agent to the target organ (see Japanese Unexamined Patent Publication (Kokai) No. 59-122423). However, since prostacyclin is chemically unstable, it has been difficult to make a lipid emulsion. Therefore, attempts have been made to make isocarbacyclin a lipid emulsion and a more effective, stable preparation having a sustained action and having a targeting effect has been developed (Japanese Unexamined Patent Publication (Kokai) No. 61-289034).
Also known are examples of use of LipoPGE.sub.1 using the form of a lipid emulsion for chronic arterial occlusion ("The Japanese Journal of Clinical and Experimental Medicine", vol. 63, p. 2423, 1986, "Cardioangiology", vol. 20, p. 331, 1986).